In FY2018, our first in human trial of PEN-866, a novel HSP90 inhibitor-SN38 drug conjugate, continued enrolling patients. The rationale for this study was based in part on preclinical work done in our lab demonstrating superior activity of PEN-866, as compared to other standard of care chemotherapy in models of pediatric sarcoma. Notably, the activity of PEN-866 was most durable in pediatric sarcoma models. For this reason, the ongoing clinical trial incorporates disease-specific expansion cohorts, including one for rhabdomyosarcoma and Ewing sarcoma, to include patients with these rare tumors. In the lab, we have continued to study PEN-866 in Ewing sarcoma and rhabdomyosarcoma, with a focus on identifying potential mechanisms of resistance.